The present invention relates to a method for producing a magnetizable metallic shaped body, to a shaped body produced by a method such as this, and to uses of such a shaped body.
Numerous magnetizable metallic bodies are known from the prior art for producing widely differing electromagnetic apparatuses, for example electromagnetic actuators, transformers or the like. These applications all have the common feature that a material which is used to produce the magnetizable components and assemblies on the one hand is intended to have good magnetic characteristics in the form of as high a (saturation) flux density as possible with low excitation and a low coercivity field strength, in which case pure iron (or materials composed of iron or of iron-silicon alloys) are particularly advantageous in respect of such magnetic characteristics.
On the other hand, particularly in the case of magnets which are operated with alternating currents (in which case the materials have their magnetization reversed in time with the alternating-current frequency), losses occur in particular in the form of eddy current losses; these are the result of voltages induced by the magnetic alternating field, producing eddy currents at right angles to the magnetic alternating field and weakening the magnetic field (also associated with an energy loss). In order to reduce such eddy current losses, it is in turn known for the magnetizable material to be influenced to increase its resistance, for example in the form of laminates in the case of transformers or by the formation of mixed crystals (for example FeNi) in magnetic material. Such an increase in the electrical resistance (resistivity) reduces the described eddy current losses but, at the same time, decreases the magnetic saturation flux density and furthermore adversely affects mechanical characteristics, such as the strength.
However, the negative effects of eddy currents are also not entirely irrelevant in the case of direct-current applications; for example, the magnetization process associated with a switching process leads to eddy currents opposing the process magnetically and limiting the dynamics and movement speed which can be achieved by actuators or the like for magnet applications using direct current.
Furthermore, eddy current losses are highly frequency-dependent, as a result of which, particularly in the case of radio-frequency applications, it is also known, for example, for powder composite materials composed of a metal powder to be used to increase the electrical resistivity, which composite materials are compressed, for example with a polymer binding agent. In addition to the relatively high electrical resistance, for example relative to a laminate, a procedure such as this furthermore has the advantage that eddy currents can be suppressed three-dimensionally. However, the magnetic characteristics of such powder composite materials are frequently inadequate, for example with a typical saturation flux density of a metal about 1.5 to about 5 times higher than that of such metal powders bonded in plastic. In this case as well, a shaped body produced in this way has poor mechanical characteristics, for example in the form of mechanical strength.
One known requirement from the known prior art is therefore to optimize the described, potentially mutually opposing, characteristics for the respective application by suitable choice and formation of the material which can be metalized, specifically by matching the magnetic characteristics which are as good as possible with eddy current losses which are as low as possible, with the necessary mechanical characteristics, for example acceptable strength.
The object of the present invention is therefore to provide a magnetizable metallic shaped body and a method for producing such a shaped body, which on the one hand makes it possible to effectively suppress or minimize energetically disadvantageous eddy currents, while on the other hand, as before, making it possible to ensure good magnetic characteristics, in particular a high magnetic (saturation) flux density and low coercivity field strength, in which case a shaped body such as this is also intended to have better mechanical characteristics (for example in comparison to known powder or sintered materials). Furthermore, suitable uses must be provided for a method such as this and shaped bodies produced in this way.